template <int Dim>
class derivative_delta
{
public:
  Tensor1<int,Dim> d_ijk_plus, d_ijk_minus;
  Tensor1<double,Dim> d_xyz;
  
  derivative_delta(double dx, double dy, double dz, int di, int dj, int dk)
    : d_ijk_plus(di,dj,dk), d_ijk_minus(di,dj,dk), d_xyz(dx,dy,dz) {}

  derivative_delta(double dx, double dy, double dz,
		   int di_plus, int dj_plus, int dk_plus,
		   int di_minus, int dj_minus, int dk_minus)
    : d_ijk_plus(di_plus,dj_plus,dk_plus),
      d_ijk_minus(di_minus,dj_minus,dk_minus), d_xyz(dx,dy,dz) {}
};
